1. Field of the Invention
The present invention relates to a novel method and system with an optional purging means for sampling fluids with entrained particles. The system is particularly applicable for monitoring particulate contamination of fluid samples using optical analysis for purposes of monitoring the condition and wear of machinery and monitoring operational parameters.
2. Description of the Related Technology
There exist a number of particulate fluid sampling systems and methods that may be operated in conjunction with an optical sensor. These systems and methods are used for a variety of different applications. Particulate monitoring is particularly important to monitoring and maintenance of machinery, especially where functional fluids are employed. For example, the analysis of debris particles in lubricating oil is a well-known method of monitoring the condition of oil wetted machinery. Particulate monitoring is also an essential maintenance procedure for hydraulic systems.
Particle fluid sampling systems may generally be categorized as either manual sampling systems and online analyzer systems. Traditionally, particulate monitoring involved manually withdrawing a sample of particle entrained fluid and transporting it to a laboratory for analysis. After reaching the laboratory, the samples had to be prepared for microscopic analysis using conventional methods such as centrifugal separation, separation onto a filter patch and ferrography. Only then was it possible to evaluate the level of particulate contamination by performing tests such as particle counting and microscopic analysis of debris particles. An expert then examined the particulates and the machine condition at the time the sample was taken is subjectively evaluated.
Unfortunately, this procedure is inefficient, time consuming, expensive and has limited effectiveness. Among the deficiencies of this conventional fluid sampling method are the long delays between sample extraction and obtaining an analysis of the sample, the necessity of sample preparation, inaccuracies resulting from subjective evaluation of samples and the fact that sampling often provides non-representative samples of the fluid since such samples are generally taken from drain ports or sumps. Additionally, the mere fact that the sample must be manually extracted substantially contributes to the inefficiency and expense of the process.
Online analyzer systems, such as online oil debris analyzers, by contrast, allow for sample analysis without requiring the manual extraction of a sample. Most of the online debris monitors, however, function to detect magnetic or ferromagnetic particles by using inductive, eddy current or magnetic interactions and provide only limited information about the debris particles. While systems such as the LaserNet Fines online optical debris monitor, described in U.S. Pat. No. 5,572,320, may be more robust and provide more data analysis, these online systems are similar in that they cannot be used to analyze non-magnetic or non-ferromagnetic particles.
U.S. Pat. No. 5,619,333 is another example of an online analyzer. It discloses a sampling apparatus, an optical analysis means and a method for monitoring particulate contamination of hydraulic fluids which may be employed to sample a high pressure stream of fluid. The apparatus includes an optical analysis means and a double acting piston for extracting particle entrained fluid samples. The fluid sampling system includes two connections to the hydraulic fluid apparatus, one on either side of the double-acting piston, such that samples can be drawn from either connection and fluid pressure of an incoming sample can be employed to equalize pressure applied to a sample on the other side of the double-action piston which is being returned to the hydraulic system. As a result, system pressure is inconsequential to operation since the fluid sampling system acts with controlled low differential pressure on both sides of the piston. This piston driven fluid sampling system, however, is limited by a fixed flow rate and flow volume and is therefore incapable of adapting to the requirements of different optical sensors and different fluid flow systems, thereby requiring a custom design for each fluid system. For this reason, it is also inefficient in extracting and expelling fluid samples. Moreover, the disclosed system does not include purging lines for cleaning the sample extraction system.
U.S. Patent application publication no. US 2006/0070426 A1 discloses another optical online analyzer adapted for field analysis at high temperatures and pressures. The system includes a sample manifold and a pressure intensifier, such as a piston, for withdrawing samples from a high pressure system.
Fluid sampling systems are also typically incapable of regulating pressures so as to adjust to different fluid flow systems. Furthermore many fluid sampling systems are incapable of operating in high pressure fluid flow systems, and thus are limited to analyzing low pressure fluid flow systems or a low pressure portion of a fluid flow system, samples of which may not be representative of the overall system condition.
Therefore, there exists a need to provide a system and method for sampling and/or purging fluids with entrained particles that offers flexibility in working with different types of optical sensors and different fluid flow systems. There also exists a need to develop a system capable of regulating fluid flow pressure which enables online analysis of both magnetic/ferromagnetic and non-magnetic/ferromagnetic particles.